DE1258721B - Binders for paper coating slips - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

D 21h

German KL: 55 F-15/20

Number: 1 258 721

File number: B 75688 VI b / 55 f

Filing date: March 3, 1964

Open date: January 11, 1968

The invention relates to binders for paper coating slips based on polymers. she relates in particular to binders obtained by mixing two different dispersions will.

Paper coating slips of the type used for the production of coated printing papers exist essentially from a suspension of a pigment or filler, e.g. B. kaolin or titanium dioxide, in an aqueous medium containing a binder.

Whereas previously only high-molecular natural products such as starch or Casein, have been used, synthetic, high molecular weight products have recently been used for this purpose, mostly in the form of aqueous dispersions, alone or in a mixture with the natural products mentioned.

Binders based on natural products have the disadvantage that they are not always the same Quality accrue, are sensitive to the infestation of microorganisms, through complex processes have to be unlocked and result in brittle strokes of mostly low water resistance.

Binders based on synthetic high polymers do not have the disadvantages mentioned.

The application of the paper coating slips to paper is usually carried out with the ones commonly used in the paper industry Devices, such as brush, air brush, roller or knife coating systems, made. The roller coating process is used particularly often because this method of working is smooth in the Can incorporate the papermaking process on the paper machine. Requirements for processability after the roller coating process, the coating slips have good flowability and stability the shear stresses occurring between the applicator rollers, otherwise coagulate will form and deposits on the rollers arise, so that a continuous and even application of the mass on the paper is no longer possible.

Paper coating slips that only contain binders based on synthetic high polymers are sufficient in general, does not meet the requirements for roller coating processes, especially if the binder content, based on kaolin, is below 10%.

So are z. B. the binders for paper coating slips known from British patent specification 751729, which are not acrylic ester copolymers are not available for processing Just as unsuitable for high-speed roller coating machines as is the case in the USA patent 2,790,735 known acrylic ester or methacrylic binders for paper coating slips

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, 6700 Ludwigshafen

Named as inventor:

Dr. Hermann Weßlau,

6702 Bad Dürkheim-Seebach;

Dr. Heinz Pohlemann, 6703 Limburgerhof;

Dr. Herbert Spoor, 6704 Mutterstadt;

Dr. Günther Addicks,

Dr. Immo Reinbold, 6700 Ludwigshafen

ester copolymers which can contain up to 40% of styrene in polymerized form, specifically especially when these binders are used without added casein.

It has now been found that you can neutral or alkaline paper coating slips, which also after Roller coating processes are processable and have excellent properties, if one Binder based on a mixture of an emulsion copolymer A with a glass transition temperature between - 60 and + 20 ° C and an emulsion copolymer B made of 15 to 55 percent by weight acrylic and / or methacrylic acid, optionally up to 10 percent by weight of acrylic and / or methacrylamide and 85 to 45 percent by weight of other water-insoluble homopolymers forming monomers, of which at least 20 percent by weight, based on the hydrophobic monomers, esters of acrylic acid or methacrylic acid with alcohols containing 1 to 4 carbon atoms are used. These new binders are characterized in that the mixture of emulsion copolymers 95 to 60 parts by weight of at least one copolymer A composed of 40 to 70 parts of styrene, 30 to 60 parts of one Esters of acrylic or methacrylic acid with alcohols that contain 2 to 12 carbon atoms in the chain and optionally up to 10 parts of other ethylenically unsaturated copolymerizable compounds and 5 to 40 parts by weight of at least one copolymer B contains.

For the copolymer A suitable esters of acrylic acid or methacrylic acid are, for. B. ethyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-dodecyl acrylate as well as the corresponding methacrylates, especially

709 718/398

3 4

special n-butyl acrylate, i-butyl acrylate and 2-ethyl hydrophobic monomers for the production of the copoly-

hexyl acrylate. merisates B exclusively or predominantly acrylic

As further ethylenically unsaturated compounds, acid and methacrylic acid esters of the aliphatic

which are used in amounts of 0 to 10 percent by weight of the on alcohols with 1 to 4 carbon atoms,

construction of the copolymer A can be involved, S The copolymers A and B can come from poly z. B. acrylonitrile, vinyl chloride or vinyl merization of the monomers in an aqueous emulsion lidenchlorid in question. In particular, the poly can be used according to methods known per se

merisat also small amounts of polar monomers one of the usual anionic and / or nonionic

contain polymerized, e.g. B. acrylic acid, methacrylic emulsifiers, z. B. of n-dodecyl sulfone

acid or crotonic acid, or amides, mono- and io acid potassium, isooctylbenzenesulfonic acid sodium,

Dialkylamides, methylolamides or methylolamide- a p-iso-

ethers of these acids, also maleic acid, fumaric acid, octylphenol, sodium laurate, etc., in amounts of

Itaconic acid and the hemiamides, the N-substituting about 0.5 to 5 percent by weight, based on the to

th half-amides or the half-esters of said polymerizing monomers, be prepared,

polybasic unsaturated acids. Particularly suitable polymerization initiators can be customary

suitable monomers of the type are acrylic acid, meth- radical-forming compounds such as peroxides, per-

acrylic acid, acrylamide and methacrylamide. Except sulphates or azo compounds, for example potassium

Strongly acidic monomeric compounds such as persulfate, cumene hydroperoxide or azo diisobutter

gene, such as vinyl sulfonic acid or styrene-p-sulfonic acid amide, in amounts between about 0.02 and 2 Ge

acid contribute to the structure of the copolymer A. 20 percent by weight, based on the monomers,

It is also possible to use mixtures of the above. The polymerization temperatures used in the

named monomers are used in the polymerization approach to the preparation of the copolymers,

add. However, the sum of their proportions should always be in the usual range, i.e. between

10 percent by weight of the copolymer A does not see about 50 and 90 ° C. You can lower

exceed. 25 genes, if you use redox catalysts or active

The composition of the monomer mixture, fourth initiator systems, e.g. B. with a system from which is used to produce the copolymer A, he potassium persulfate and ascorbic acid, oxymethane drives a restriction by the following condition: sulfonic acid sodium or triethanolamine works. The glass transition temperature of the polymer A should be- to regulate the molecular weight can see are -60 and +20 ⁰ C. (For a definition of the 30 usual chain carriers, e.g. n-dodecyl mercaptan, glass transition temperature, see PJ Flory, Principles of Polymer Cyclohexene or carbon tetrabromide, in amounts Chemistry, Cornell University Press, Ithaca, New of about 0.05 to 0.5 percent by weight , based on York, 1953, p. 56.) This condition has its one of the monomers, used to be
luminous justification in the fact that the dispersions can, as is well known, in almost polymer A the main component of a binding 35 arbitrarily small concentrations, z. B. represents in a Konmittelgemisches for paper coating slips. It has a concentration of 0.5 percent by weight and must therefore be produced at temperatures around or only a little. This does not make economic sense, however, since it is still plastically deformed above room temperature, especially in view of the need to be bar so that the finished paper coating can be smoothed on the usual dispersions over longer distances to be transported. All polymers. Therefore, the preferred concentrations that do not meet the stated condition are between 20 and 60 percent by weight,
are not suitable for the binding agents according to the invention. The binding agent according to the invention for paper agents. So has z. B. a copolymer, which coating slip contains a mixture of the co-produced by copolymerization of 60 polymer A and the copolymer B. Here, parts by weight of styrene, 38 parts by weight of tert-butyl 45, the mixing ratio should be chosen so that acrylate and 2 parts by weight of acrylic acid, one of which is applied to the solids, 95 to 60 parts by weight of the glass transition temperature above 20 ° C. and is therefore unsuitable as copolymer A in addition to 5 to 40 parts by weight of the possible copolymer A. Copolymers B are very suitable in the finished mixture, and copolymers A are preferred, however. Preferred mixtures contain 90 to 40 to 60 parts of n-butyl acrylic ester and / or 50 to 70 parts by weight of copolymer A in addition to 10 isobutyl acrylic ester, 60 to 40 parts of styrene and up to 30 parts by weight of the copolymer B.
0 to 5 parts of acrylic acid or methacrylic acid. To achieve the desired technical efficiency

According to the invention, it is unimportant in terms of the structure of the copolyfect whether the mixing process takes place before merisates B 15 to 55 percent by weight acrylic or or during the production of the coating color instead of methacrylic acid, 0 to 10 percent by weight, especially 55 finds. Also the order in the union of the Their 2 to 6 percent by weight, acrylic or methacrylic components of the coating color are irrelevant amide and 85 to 45 percent by weight hydrophobic, for the properties of the coating slip or the water-insoluble Mono-coated paper forming homopolymers. But it is still an advantage mers, of which at least 20 percent by weight when considering the aqueous dispersions of the copolyesters the acrylic or methacrylic acid with aliphatic 60 merisate A and B before the production of the coating tables Alcohols are 1 to 4 carbon atoms in mass mixes in the desired proportion included, be involved. As more hydrophobic, and the finished mixture is kept. The two Ethylenically unsaturated compounds come, for. B. Dispersions are namely excellent with each other Acrylic and methacrylic acid esters are more aliphatic compatible, especially when both dispensing tables, cycloaliphatic or aromatic hy- 65 sions are mixed as they are with the common hydroxyl compounds, Styrene, vinyl chloride, vinylidene emulsion polymerization incurred, and the im chloride, especially vinyl acetate, vinyl propionate or copolymer does not contain carboxyl groups Acrylonitrile, in question. However, they are preferably neutralized before the mixing process. This ge

Mixtures are completely stable and can easily be used in concentrations up to a solids content of over 50 percent by weight can be produced. They remain thin until you add a base, such as ammonia or sodium carbonate, neutralizes the carboxyl groups present. If you take the Neutralization only occurs when all proportions of the coating mix except for the alkali are homogeneous are mixed with one another, there is the technically significant advantage that there are no highly viscous ones Must transport materials, but only thin, d. H. pumpable, like the binder mixture, and solid like the pigment used.

If you mix z. B. 77.25 parts by weight of a 50% Dispersion of the copolymer A composed of 49 percent by weight styrene, 49 percent by weight n-butyl acrylate and 2 percent by weight of acrylic acid with 22.75 parts by weight of a 30% dispersion of the copolymer B from 75 percent by weight of ethyl acrylate, 20 percent by weight of acrylic acid and 5 percent by weight Acrylamide, a mixture is obtained that contains 45 percent solids by weight. The solid consists of 85 parts by weight of the copolymer A and 15 parts by weight of the copolymer B. Die The viscosity of the mixture is 18 cP, measured with a Brookfield viscometer, system 5 20 revolutions per minute. After adding 2 parts by weight of 2% strength ammonia water 100 parts by weight of the mixture this goes into one hardly flowable paste over. On the other hand, 100 parts by weight of the mixture are first diluted by addition from 50 parts by weight of water to a solids content of 30.5 percent by weight and then continues 2 parts by weight of 25% ammonia water, the viscosity of this mixture is 15,300 cP, measured with the Brookfield viscometer, system 200.

According to the invention, the polymer mixtures are outstanding as binders for the production of Paper coating slips suitable. They are known in and of themselves before being used for painting Way with fillers, especially with clay or titanium oxide and optionally other auxiliaries mixed and by adding alkali, e.g. B. sodium or potassium hydroxide, but preferably Ammonia, neutralized. The finished paper coating slips can by all known methods Base papers are applied. Their particular advantage, however, is their extraordinary high shear stability, which is the preferred processing by the technically particularly simple roller coating process suggests, on the other hand, in the high binding power of the polymer mixture, the binder content of only 6 to 8 percent by weight, based on sound, allowed. They are also characterized by their even course, their resistance against bacterial infestation as well as by the water resistance and smoothness of the finished coat. the Art paper produced with them have excellent printing properties.

The parts mentioned in the following examples are parts by weight.

example 1
a) Preparation of a dispersion of copolymer A.

1050 parts of styrene, 1050 parts of n-butyl acrylic acid and 42 parts of acrylic acid are placed in a stirred vessel and 10 parts of sodium vinyl sulfonate together with 42 parts of an addition product of 25 moles Ethylene oxide on p-isooctylphenol, 84 parts of a similar addition product, which has been mixed with sulfuric acid, and 9.6 parts of potassium persulfate emulsified in 1960 parts of water. This mixture is heated at 80 to 85 ° C. for 4 hours entered with stirring in a polymerization vessel in which 180 parts to 80 ° C. at the beginning ίο there is preheated water. After adding 1.5 parts of potassium persulfate in 60 parts of water polymerized at 85 ° C. An approximately 50% polymer dispersion is obtained.

'5 b) Preparation of a dispersion of copolymer B

345 parts of water, 0.6 parts of potassium persulfate and 1.5 parts of p-isooctylbenzenesulfonic acid are placed in a polymerization vessel Submitted sodium and 0.1 part of sodium pyrophosphate and heated to 85 ° C. In this solution one leaves in the course of A mixture of 112.5 parts of ethyl acrylate, 30 parts of acrylic acid, 7.5 parts of acrylamide for 2 hours and 0.08 part of dodecyl mercaptan are poured in with stirring. Then about 30 minutes at Polymerized at 90 ° C. and steamed for a further 15 minutes while passing in nitrogen.

An approximately 30% polymer dispersion is obtained with a K value (H. Fikentscher, Cellulosechemie, 13 [1932], p. 60) of the polymer of 68 (1% strength measured in cyclohexanone) and a viscosity of 14 seconds (measured in a DIN cup 4 mm).

c) Production of the paper coating slip

In an aqueous solution of 0.3 parts of sodium polyacrylate are with the aid of a high-speed stirrer 100 parts of china clay are stirred in. As a binder, 18.6 parts of a mixture of 75 parts of the after a) and 25 parts of the polymer dispersion prepared according to b) are added and the coating color is added Ammonia adjusted to pH 8. At a solids content of 45 percent by weight and a temperature of 20 ° C, the coating slip has a viscosity of 1000 cP (Brookfield viscometer, 20 rpm).

The paper coating slip produced in this way is applied with the help of a roller applicator between two rubber rollers of different hardness at a line pressure of 15 kg / cm on a paper with a composition of 70% wood pulp, 30% bleached sulfite pulp, 0.4% resin and 4% Alum, an ash content of 20% and a basis weight of 80 g / cm ² applied. Even after a long period of operation, no coagulum or coating forms on the rollers. The coated and satined paper impresses with its gloss and smoothness and has excellent printing properties, especially in gravure printing.

A paper coating slip, which with 16 parts of the dispersion prepared according to a) alone in otherwise produced in the same way, has a viscosity of 21 cP at 20 ° C (Brookfield viscometer, 20 rpm). When applying this mass to the paper, form according to the above procedure After a few minutes, thick deposits form on the rollers, making an even application impossible is.

Example 2

The coating slip is made as in Example I _3, however, the binder, based on china clay, is 16.3 parts of a mixture consisting of 70 parts of a 50% dispersion of a copolymer of 45 parts of isobutyl acrylate, 53 parts of styrene and 2 parts Acrylic acid and 30 parts of the copolymer dispersion described in Example 1 under b) are used.

The 45% coating slip has a viscosity of 1000 cP at 20 ° C (Brookfield viscometer, 20 rpm) and can be processed just as easily as the coating slip from Example 1.

Example 3

To produce a 60% coating slip, 100 parts of china clay are stirred into an aqueous solution of 0.3 part of sodium polyacrylate in 62 parts of water using a high-speed stirrer. 17.6 parts of a mixture of 85 parts of the polymer dispersions prepared according to Example 1, a) and 15 parts of the _{polymer dispersions prepared according to Example I 3} b) are added to the pigment slurry as binder.

The coating slip is adjusted to pH 8 with sodium hydroxide solution and has a pH of 20 ° C Viscosity of 2400 cP (Brookfield viscometer, 20 rpm). The coating can be used with Apply to paper using a doctor blade coater.

Claims (1)

8th
Claim: Binder for neutral or alkaline paper coating slips based on a mixture of an emulsion copolymer A with a glass temperature between -60 and +20 ⁰ C and an emulsion copolymer B of 15 to 55 percent by weight of acrylic and / or methacrylic acid, optionally up to 10 percent by weight of acrylic and or or methacrylamide and 85 to 45 percent by weight of other water-insoluble homopolymers forming monomers, of which at least 20 percent by weight, based on these hydrophobic monomers, esters of acrylic acid or methacrylic acid with alcohols containing 1 to 4 carbon atoms, characterized in that the mixture 95 to 60 parts by weight of at least one copolymer A composed of 40 to 70 parts of styrene, 30 to 60 parts of an ester of acrylic or methacrylic acid with alcohols containing 2 to 12 carbon atoms in the chain, and optionally up to 10 parts of other ethylenically unsaturated, copolymerizable Connections and 5 to 40 G contains at least one copolymer B by weight. Considered publications:
U.S. Patent No. 2,790,735;
British Patent No. 751 729. 709 718/398 12.67 © Bundesdruckerei Berlin